ABSTRACT
Following our procedure of slowly introducing complexity into the description of projectile behavior we shall now develop equations to characterize the remainder of what is known in general as swerve motion. We saw in Chapter 11 that a mass asymmetry can cause projectile motion transverse to the original line of fire even in a vacuum. We stated in that section that a dynamic projectile imbalance was more common than a static imbalance but either can actually occur. Chapter 6 explained many aspects of projectile behavior that arise due to the presence of
the air stream. All of the coefficients were functions of the angle of the attack observed by the projectile relative to that air stream. If we examine how a statically or dynamically imbalanced projectile would behave as viewed from above the trajectory curve based on its spin, we would see motion as depicted in Figures 12.1 and 12.2. We must keep in mind that the motion in these figures is greatly exaggerated for ease of viewing. We can imagine, by looking at these figures that the aerodynamic forces would be
considerable because even in the case of the statically imbalanced projectile, motion laterally across the trajectory will manifest itself in an angle of attack and therefore affect the flight characteristics. In this section, we shall describe and evaluate the aerodynamic forces that arise from this
behavior and include them in our equations of motion for projectile flight. We shall also include the effect of configurational asymmetries such as bent fins or damaged form because these will result in similar behavior even without the mass asymmetry present. In fact, to a varying degree, every projectile has a combination of both form and mass asymmetries present.
